Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie
2019 Atlantic Hurricane Season
Comments
-
-
-
-
-
-
Advertisement
-
-
-
-
-
-
Advertisement
-
The parallels with 2004 will be interesting to see once this season ends. It got off to a later start thanks to Saharan dust, but the Modoki El Nino phenomenon has had more or less the same result - a back-loaded season in which wind shear plummeted across the basin as the summer progressed.
For comparison:
I'm not entirely sure on the mechanics of how this SST setup in the Pacific enhances the Atlantic hurricane season, but it seems to have two components - one is, fairly straightforwardly, that increased convection West of the date line generates upper-level outflow, which travels Eastward before sinking over the Eastern Pacific and choking tropical disturbances and thunderstorms in that area. Consequently, upper-level outflow from the Eastern Pacific, which would normally suppress the Atlantic to some degree in the same manner, is reduced.
However, the second component is beyond my current level of understanding - the SST setup affects the Walker Circulation in a way which reduces upper-level wind shear over the Atlantic when El Nino conditions are displaced into the Central rather than the Eastern Pacific. This is partly what led to such an extreme hurricane season in 2004 and subsequently the record breaking season in 2005 - this pattern, in combination with the ongoing positive AMO phase, allowed major hurricanes to spin up in July 2005 where normally wind shear and subsidence from Eastern Pacific storms' outflow would choke most tropical waves before they have a chance to build a closed circulation.
If this pattern holds, it wouldn't surprise me to see this season continuing to be extremely active into the Winter, followed by an early burst of activity next summer, similar to 2004 and 2005 respectively. The only factor which is out of sync is the PDO, which is a lot higher now than it was in the 2000s - but as evidenced by 2017, the PDO isn't nearly as influential as ENSO when it comes to Atlantic tropical cyclogenesis.0 -
-
-
-
Just some observations about the track of what will be left of Lorenzo ( by then probably an Ex Tropical cyclone ) when it moves further N towards us.
ECM has been very consistent in taking the system well off the W coast now for a number of days. The latest run a bit closer but still keeping the strongest winds well off shore. GFS now looking more like the ECM ,GEM resembling the same track also.
The three models mentioned go on to show the remnants of Lorenzo being absorbed into a large area of LP initially taking the system well away from Ireland.
Currently at over 7 days out looks like a powerful storm when it reaches off the SW / W . A lot could change but worth keeping a daily log of what the models are projecting . Would need to keep an eye on rainfall also.
0 -
-
-
-
All >=115kt hurricanes since 1960 on or after 26th September. Unless I've made a howler in analysing the data, #Lorenzo is quite an anomaly.
credit:
https://twitter.com/catinsight0 -
-
Advertisement
-
-
JanuarySnowstor wrote: »Needs watching as it's only a hares breath from a direct hit. While it remains modelled to our West overall concensus today is to move it closer to our shore than what was previously thought
Do you mean a " hair's breadth"? Maybe your version is more interesting! And sure, what is one more gale here! As she listens to wind and rain battering the dwelling..
0 -
-
-
Meanwhile, Typhoon Mitag is spinning up northeast of Manila and looks like brushing by Taiwan, Shanghai and making landfall in South Korea as a Cat 1 next Wednesday. For a while it was looking a little further east and slower, possibly coming closer to Kobe, where Ireland will play Samoa on Thursday.
0 -
-
The 2019 Atlantic season was extremely quiet up to the last week in August, but then spung to action and generated several named storms, two of which reached Cat 5 status (Dorian and Lorenzo). This timing perfectly matched the climatological peak activity, which is centred around September 10th.
The reasons for the enhanced activity are primarily the ENSO-nuetral conditions, the timing of Madden Julian Oscillation (Phase 1 occuring right at that time) and the warm phase of the Atlantic Multidecadal Oscillation (a natural warming of waters in the North Atlantic, which is known to enhance tropical activity).
Lorenzo had the best possible conditons to rapidly intensify;
-it developed in the an area typical for the time of year (MDA)
-it was passing over a warm anomaly of SST due to the warm AMO (although the depth of this warmth (ocean heat content) was a little lower than typically needed for rapid intensification),
-perfect timing of the spike in MJO, which enhanced convection in that particular area. At the same time the activity decreased in the western Atlantic, with Humerto, Jerry and Karen fizzling out),
-low wind shear in the area due to the MJO and ENSO neutral conditions.
These factors were enough to overcome some dry air and marginal ocean heat content. The approach of the NW Atlantic trough later on helped vent the storm poleward and keep pressure lower than it otherwise have been as it accelerated towards the Azores.
The ECMWF forecasts the MJO to remain in Phase 1 for the next couple of weeks but at a lower amplitude than during September. The SST have reduced and the main development region retreats back west towards the Caribbean.
0 -
-
-
Advertisement
-
Advertisement